Fixed-dried red blood cells

ABSTRACT

Fixed-dried red blood cells (RBCs), and processes for preparing the same are disclosed. The red blood cells, upon reconstitution with distilled water or appropriate buffer: bind oxygen with native affinities, have partial deformability, present minimal thrombogenicity to platelets, and have oblated blood group antigens. The RBCs are preferably fixed by means of cross-linkers with aldehyde functions such as paraformaldehyde or glutaraldehyde either alone or in combination. Native oxygen kinetics are achieved by preparing the red blood cells with 1,6-diphosphofructose. Blood group antigens and chemical functions that render the lyophilized RBCs thrombogenic are occluded by chemically attaching polyoxyethylene glycol polymers to the surface membrane of the red blood cells. The cross-linked red blood cells are preferably died by lyophilization.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/316,674, filed Aug. 31, 2001, the disclosure of which isincorporated by reference herein in its entirety.

STATEMENT OF FEDERAL SUPPORT

This invention was made with Government support under grant numberN00014-97-1-0867 from the Office of Naval Research. The Government hascertain rights to this invention.

FIELD OF THE INVENTION

The present invention relates to methods, based on stabilization ofcellular structures with chemical cross-linkers and lyophilizaton, forpreparing human and other mammalian species red blood cells for storagefor allographic (same species) and xenographic (across species)transfusion for medical purposes.

BACKGROUND OF THE INVENTION

The use of red blood cell (RBC) concentrates for providing oxygencarrying capacity in transfusion medicine is well established forapplications that include in the treatment of anemias and hemorrhagictrauma. Red blood cells can be stored for up to 42 days under currentAABB guidelines at reduced temperatures as detailed by Menitove, J. eds(1999) Standards for blood banks and transfusion services, 19th ed.Bethesda, Md.: AABB. Technologies have been developed for thecryopreservation of RBCs for long-term storage in the frozen state thatrequire post-thawing steps to remove the RBCs from cryopreservativesbefore infusion (Vengelen-Tyler, V. eds. (1999) AABB Technical Manual,p. 178 13th ed. Bethesda, Md.: AABB). In order to minimize thelogistical complexities of blood banking fresh and cryopreserved RBCs,we have developed methods for preparing lyophilized RBCs with aprolonged shelf-life for infusion after simple rehydration with H₂O orbuffer.

Two methods have been described previously for the preparation oflyophilized RBCs. First, Goodrich et al. (Proc. Natl. Acad. Sci. USA(1992) 89, 967-971; U.S. Pat. No. 4,874,690) outline methods forfreezing RBCs in the presence of monosaccharides, polyanions andpolymers and drying by sublimation of water. Post-hydration processingis required to remove the cryopreserving agents. Secondly, Bakaltchevaet al. (2000) Cryobiology 40, 343-359 describe procedures forstabilizing RBCs with the reversible chemical cross-linker dimethyl3,3-dithiobispropionimidate and then freezing the cells in the presenceof glucose as a cryopreservative with hemoglobin ligated by carbonmonoxide. After freeze-drying and lyophilization, the cells arerehydrated and the cross-linker is reversed with dithioerythritol torestore approximately native osmotic fragility and deformability.

SUMMARY OF THE INVENTION

The present invention provides methods for the stabilization of cellularstructures with chemical cross-linkers and lyophilizations in thepreparation of red blood cells for long-term storage.

Accordingly, a first aspect of the present invention is fixed-driedmammalian red blood cells containing exogeneous fructose1,6-diphosphate, preferably in an amount effective to enhance the oxygencarrying capacity thereof (e.g., the cells have an oxygen-carryingcapacity greater than would the same cells in the absence of exogeneousfructose 1,6-diphosphate).

A second aspect of the present invention comprises fixed-dried mammalianred blood cells having a water-soluble polymer covalently coupled to thecell membrane thereof.

A third aspect of the present invention is a method of makingfixed-dried mammalian red blood cells, comprising the steps of providingmammalian red blood cells, cross-linking the red blood cells, thenfreezing said red blood cells at ambient or elevated pressuressufficient to form ice II, ice III, ice V or ice VI therein; and thendrying said frozen cells to produce said fixed dried mammalian red bloodcells. Cells produced by the foregoing method are also an aspect of theinvention.

A further aspect of the present invention is the use of cells asdescribed above for the preparation of a composition or medicament foradministration to a subject to administer red blood cells to thesubject.

A further aspect of the present invention is a formulation comprisingred blood cells as described above reconstituted in an aqueous carriersolution.

A still further aspect of the present invention is a method ofadministering red blood cells to a mammalian subject, comprisingreconstituting red blood cells as described above in an aqueous carriersolution, and then administering the reconstituted red blood cells tothe subject.

The foregoing and other objects and aspects of the present invention areexplained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—The trajectory for hyperbaric preparation of rehydrated,lyophilized red blood cells.

FIG. 2—The normal size and shape morphology of rehydrated RBCs as imagedwith scanning electron microscopy for cells prepared as detailed inexample 1.

FIG. 3—The normal ultrastructural morphology of rehydrated RBCs asimaged with transmission electron microscopy for cells prepared asdetailed in example 1.

FIG. 4—Titration of hemoglobin oxygen affinity with1,6-diphosphofructose as described in example 2.

FIG. 5—Reduction of surface thrombogenicity of lyophilized RBCs withcovalent PEG 5,000 attachment.

FIG. 6—Occlusion of blood A antigen with covalent attachment of PEG5,000.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a”, “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise.

“Mammalian” as used herein, refers to both human and animal subjects andhuman and animal blood cells, such as dogs, cats, horses, pigs, cows,rabbits, goats and the like. Thus the present invention may be used inboth human medical and veterinary medical applications.

The present method of RBC stabilization with aldehyde-based chemicalcross-linkers has been used to prepare lyophilized platelets that retainmany aspects of native function (U.S. Pat. No. 5,651,966) It wasdemonstrated that with mild aldehyde cross-linking, rehydrated,lyophilized (RL) platelets have a near normal ultrastructure by electronmicroscopy and retain many of the surface membrane functions of freshplatelets (Read et al. (1995) Proc. Natl. Acad. Sci. USA 92:397-401). RLplatelets adhere to denuded subendothelium, spread on foreign surfaces(Read et al. (1995) Proc. Natl. Acad. Sci. USA 92:397-401) and theglycoprotein IIb-IIIa and Ib-IX complexes respectively bind fibrinogen(Sanders et al. (1996) Blood 88:S107) and von Willebrand factor(Khandelwal et al. (1997) FASEB J. 11:1812). It was also demonstratedthat RL platelets catalyze the conversion of prothrombin to thrombin and(U.S. Pat. No. 5,651,966). Read et al. conducted in vivo experiments inwhich RL platelets decrease bleeding times in thrombocytopenic rats andparticipate in thrombus formation in a canine model system (Read et al.(1995) Proc. Natl. Acad. Sci. USA 92:397-401). It was also shown thatintracellular stimulus-response signaling was operant in RL platelets(Fischer et al., (2000) Brit. J. Haem. 111, 167-175).

Both the protein kinase C (PKC) and myosin light chain kinase (MLCK)signaling were stimulated in RL platelets in response to activatingagents. This finding was important because of the role PKC and MLCK playin orchestrating the aggregation and clot retraction. These resultsdemonstrated that RL platelets are not simply “circulating membranes”,but can be activated. The cross-linker was required for preparinglyophilized RBCs and platelets because the transition from the liquid toice phase state (for the ice I phase) results in an approximately 8%expansion in volume that ruptures membranes and distorts intracellularstructures (see, for example, Dahl and Staehelin (1989) J. ElectronMicr. Tech. 13:165-174). This invention provides methods for stabilizingthe structure of RBCs prior to freezing so as to minimize damage due toice crystal expansion.

An alternative, or complementary, method for minimizing damage from icecrystal expansion is to freeze into and lyophilize RBCs from highpressure phase states of ice. Defined by Bridgman, P., (1935) J. Chem.Phys. 3, 597-603, the high pressure phase states of ice (Ice III, IceII, Ice IV, Ice V and Ice VI) are denser than water. The ice III and iceIII phase states are the lowest pressure forms, with an approximatelyisothermal transition point at temperatures less than −20° C. andpressures of 2000 atmospheres (Bridgman, P. (1935) J. Chem. Phys.597-603). The ice II/III phase states are metastable at temperaturesbelow −120° C. (Bertie, J., Calvert, L. and Whalley, E. (1963) J. Chem.Phys. 38, 840; Dowell, L. and Rinfret, A. (1960) Nature 188, 1144) andexert finite vapor pressures for lyophilization (Livesey et al. (1991)J. Microscopy 205-215). Lyophilization from ice II/III phase states havebeen accomplished through “molecular distillation” methods as describedby Livesey et al. (1991) J. Microscopy 205-215. Three lines of evidenceindicate that red blood cells can be subjected to and frozen at elevatedpressures with retention of viability. First, electron microscopistshave noted with many types of mammalian tissues that hyperbaric freezingat the liquid→ice III transition minimizes the extent of structuraldistortion due to ice I crystallization (see Monaghan, et al. (1998) J.Microscopy 192:248-258 or Dahl and Staehelin (1989) J. Electron Micr.Tech. 13:165-174 for a review). Secondly, barophilic bacteria have beenisolated from deep-sea trenches with optimal growth at 700 atm. Thisresult indicates that phospholipid bilayer, chromatin, and othersupramolecular structures are stable at 700 atm, and might also retainnative functions at higher pressures. Finally, the pressures needed forthe formation of ice III, V and VI (see FIG. 1) do not cause wholesaleprotein denaturation (see Carter, et al. (1971) Cryobiology 8:524-534;Goossens et al. (1996) Eur. J. Biochem. 236:254-262; and Wroblowski etal. (1996) Proteins: Structure, function and genetics 25: 446-55, andfor a general review, Silva and Weber (1993) Ann. Rev. Phys. Chem.44:89-113).

An early realization in the development of hemoglobin-based oxygencarriers was that an effect of covalently cross-linking hemoglobin wasto increase the oxygen affinity of the protein out of the physiologicalrange [e.g., Pietta et al., (1984) Pietta, P., Pace, M., Palazzini, G.and Agostoni, A. (1984) Prep. Biochem. 14, 313-329). This affinityincrease could be due to modifications of the 2,3-DPG binding siteand/or a “locking” of hemoglobin in the high O₂ affinity conformationstate. We obtained a similar result when RBCs were stabilized forlyophilization by aldehyde cross-linking; oxygen affinity shifted from anormal value of 27 torr to 7 torr. We have shown (Fischer et al. (2000)Blood 94, 2838) that the hemoglobin affinity for oxygen can be directlymodulated by preparing RL RBCs with 1,6-diphosphofructose, the upstreamsource of 2,3-DPG. 1,6-diphosphofructose has previously been used toameliorate reperfusion injury by providing an anaerobic energy sourceduring ischemia (Takeuchi et al., (1998) J. Thor. and Card. Surg. 116,335-343; Sano et al., (1995) Gastroenterology 108, 1785-1792). Bytitrating the RBCs with increasing concentrations of1,6-diphosphofructose we are able to fine-tune the oxygen affinityhemoglobin in RL RBCs to values between 10 and 50 torr.

Polyoxyethylene glycol (PEG) polymers have been extensively used tosterically occlude theraputic proteins (e.g., Roberts, M. and Harris, M.(1998) J. Pharm. Sci. 87, 1440-1445)) and liposomes (Lasic, D. (1996)Liposomes. Sci. Med. 3, 34-43) from elements of the reticuloendothelialsystem to prolong circulation times. Several research groups report thatthe covalent attachement of PEG to the membranes of fresh RBCs so as tooccludes blood group antigens (Hortin et al., (1997) Art. Cells, BloodSubs. and Immob. Biotech. 25, 487-491; Scott et al. (1997) Proc. Natl.Acad. Sci. USA 94, 7566-7571; Armstrong et al. (1997) Am J. Hematol. 56,26-28). We extend this methodology by covalently attaching PEG polymersto the surface membrane of RBCs so as to occlude chemical functions thatmediate uptake by the reticuloendothelial system render the lyophilizedcells thrombogenic when they contact platelets.

Cross-linked and lyophilized RBCs of the present invention may beprepared with bifunctional cross-linking reagents that are homo orheteromeric with reactive the following reactive moeties: aldehydes,ketones, hydrazides, N-hydroxysulfosuccinimides, N-hydroxysuccinimides,maleimides, imidoesters, active halogens, pyridyl-disulfides,isocyanates, nitrobenzoyloxysuccinimides, nitrobenzenes, imidoesters,photo-activatable azidophenyls and azidopolyaromatics, as well aszero-spacer carbodimide catalysts. Multi (poly) functional reagents arealso considered, as are combinations of two or more cross-linkers,either serially reacted with RBCs for reacted together with RBCs.

RBCs are obtained from mammalian blood with standard phlebotomy,apheresis or exsangination methods according to approved IACCOCprotocols. RBCs are freed from plasma platelets, leukocytes and plasmaproteins my differential centrifugation, and then treated with chemicalcross-linkers. The reaction of the RBCs with the cross-linkers are ingeneral carried out for defined periods of time at temperatures between20° C. and 37° C. at pre-determined concentration of RBCs. As discussedin greater detail below, care must be taken to sufficiently fix theplatelets or undue lysis will be measured upon rehydration of thelyophilized product. The cross-linking step can be carried out in thepresence of antioxidants and free-radical scavengers, and thecross-linking reaction can be quenched by adding compounds that containprimary amines. After cross-linking, the RBCs are removed from excesscross-linker and reaction products with differential centrifugation,chromatography and/or dialysis.

Freezing of RBCs after cross-linking may be carried out over a widerange of cooling rates at ambient or hyperbaric pressures. If RBCs (withzero or reduced concentrations of cross-linkers) are frozen into thehigh-pressure phase states of ice (e.g., ice II/III) samples arepreferably isothermally pressurized and then isobarically cooled tounder −120° C., the point at which ice II/III is metastable (see FIG.1). RBCs can be frozen in the presence of “stabilizer” small molecules(e.g., glycerol), proteins (e.g., albumin) and polymers (e.g., PEG)which substitute for water in the ice crystal matrix. The perfered“stabilizer” is PEG 8,000 at a final concentration of 1% (w.v). The typeand level of “stabilizer” must be infusible as rehydrated.Lyophilization is carried out from temperatures below 0° C., preferably40° C. if the RBCs were frozen at ambient pressure for ice I, and nearor less than −120° C. for molecular distillation from the ice II/IIIphase states.

Fructose 1,6 diphosphate used to carry out the present invention isknown. See, e.g., The Merck Index, Monograph No. 4297 (12^(th) Ed.1996). 1,6-diphosphofructose is added to RBCs to adjust the oxygenaffinity of hemoglobin to defined values, preferably to the commonphysiological value of 27 torr. 1,6-diphosphofructose is incubated withthe RBCs at any step in the isolation and cross-linking procedures, andmay be included with “stabilizers” during freezing and lyophilization.1,6-diphosphofructose is preferably incubated with the RBCs for one hourbefore and then during a 20 minute cross-linking period at aconcentration of 10 mM.

The chemical modification of RBC membranes with cross-linkers imparts a“foreign” nature to the cells with respect to recognition by thereticuloendothelial system and thrombogenic with respect to contactactivation of platelets. The surface membrane is thus occluded bycovalently attaching polymers that sterically coat the cell membrane.Polymers, particularly water-soluble polymers, that may be used to carryout the present invention are, in general, naturally occurring polymerssuch as polysaccharides, or synthetic polymers such as polyalkyleneoxides such as polyethylene glycols (PEG), polyalkylene glycols,polyoxyethylated polyols, polyvinylpyrrolidone, polyacrylates such aspolyhydroxyethyl methacrylate, polyvinyl alcohols, and polyurethane. Thepolymers may be linear, branched or dendrimeric and may be substitutedor unsubstituted. The polymers may, as noted above, be hydrophilic,lipophilic, or both hydrophilic and lipophilic. Polymers are covalentlyattached through the membrane through reactive chemical functions thatinclude, but are not limited to, aldehydes, ketones, hydrazides,N-hydroxysulfosuccinimides, N-hydroxysuccinimides, maleimides,imidoesters, active halogens, pyridyl-disulfides, isocyanates,nitrobenzoyloxysuccinimides, nitrobenzenes, imidoesters,photo-activatable azidophenyls and azidopolyaromatics, as well aszero-spacer carbodimide catalysts. The preferred polymer is PEG 5,000with a terminal aldehyde for covalent attachment to surface lysines viaSchift's base formation.

In use, the fixed-dried blood cells produced by the procedures describedherein are reconstituted (i.e., rehydrated) in an aqueous carriersolution to provide a formulation which is then administered to thesubject (for xenographic or allographic infusion). The carrier solutionis, in general, a physiologically acceptable carrier solution, such assterile physiological saline solution. Generally the reconstitutedpreparation will contain from 1 or 2 up to 6, 8 or 10×10⁹ cells permilliliter. Rehydrated RBC of the invention may any disorder orcondition for which the administration of blood cells is beneficial,including but not limited to anemias and as a component of replacementfluids in hemorrhage.

In some embodiments of the invention, it is beneficial to performcertain pre-treatments of the whole blood to improve the quality of thefreeze-dried product, as set forth below.

(a). Heat-shock of the whole blood may be used to induce activation ofchaperone proteins to reduce protein denaturation during dehydration.This process involves, for example, heating the whole blood in a PL-146plastic bag at 42 C for 10-15 minutes, preferably in atemperature-controlled water bath, before beginning the washing or cellseparation steps. This treatment has been applied to whole tissues andplatelet suspensions for improved preservation in room temperature orcold storage, but has not been reported for treatment of red blood cellsin preparation for freeze-drying. (See, e.g., A E and Gabai V L; HeatShock Proteins and Cytoprotection: ATP-Deprived Mammalian Cells, Chapmanand Hall (1997)).

(b). Leukodepletion of the whole blood may be carried out by means ofcommercially available affinity filters. This process involves, forexample, passing the whole blood (after heat shock treatment ifperformed) into the input port of a Pall Purecell Neo leukoreductionfilter (or other FDA-approved filter for the purpose of adsorbing whiteblood cells out of the whole blood) and collecting the effluent in aclean closed container. The benefit from reduction of the white bloodcell count at the start is that there will be less possibility ofdegradation of red cells during further processing by enzymes or oxygenradicals released from activated leukocytes. The most often cited reasonin support of leukoreduction for banked blood components is to preventGraft-verus-Host disease from transfusion in the recipient patient, andthe effects on the stored cells has not been adequately investigated.The leukoreduction step may also be performed on the packed red cellmass retained after centrifugation separation of the whole blood intored cells and platelet-rich plasma. See, e.g., Beugeling T, Feijen J,and van Aken W G: “The Mechanisms of Leukocyte Removal by Filtration.”in Transfusion Medicine Reviews, Vol IX (No. 2): pp 145-166 (1995).

(c). Compounds may be added to the whole blood to, among other things,reduce activation of enzymes in the coagulation, fibrinolytic, orcomplement system pathways. The primary example of the instant inventionmentions a citrate-based anticoagulant based on standard formulae usedin blood banking. This formula may be supplemented with addition of, forexample, general protease inhibitors (e.g., leupeptin, aprotinin,ethylenediaminetetraacetic acid [EDTA], N-ethyl maleimide, etc), orspecific thrombin inhibitors (e.g., hirudin, heparin, Thromstop, etc),or complement convertase inhibitors (e.g. FUT-175, etc), or specificplasmin inhibitors (e.g., e-amino caproic acid, tranexamic acid, etc).These compounds have been applied to various degrees in attempts toimprove the storage of platelets for blood banking, but this has notbeen reported for applications in improving the storage of red bloodcells. See, e.g., Bode, A. P., and Norris, H. T.; “The Use of Inhibitorsof Platelet Activation of Protease Activity in Platelet ConcentratesStored for Transfusion.” Blood Cells 18: pp. 361-380 (1992).

Some important embodiments of the instant invention include deliberateincorporation of a plasticizer into the membrane of the fixed red bloodcell before dehydration in an amount sufficient to enhance or retaincell deformability at the time of subsequent reconstitution. A preferredembodiment of this feature is performed by suspending the fixed, washedred blood cells prior to freezing in a phosphate buffer containing atleast 0.1% bovine serum albumin [BSA] at a cell count of 2-3×10⁹/mL in aPL-146 storage bag held at 4 C and then introducing 1/1000^(th) volumeof a solution comprised of 20-40 milligrams/mL diethylhexylphthalate[DEHP] dissolved in absolute ethanol or dimethylsulfoxide [DMSO]. Theincubation period at 4° C. of the red cells in this solution should bebetween 48 hours as a minimum and 120 hours as a maximum. At the end ofthis incubation the red cells should be packed by centrifugation andresuspended in the bulking solutions already described and then taken tofreeze-drying. Solutions containing plasticizers such as DEHP have beenreported in the literature to impart extra stability to liquid-storedred blood cells in blood bank storage, but this has not been similarlyreported for application to a freeze-drying process. See, e.g., Estep TN, Pedersen R A, Miller T J, Stupar K R: “Characterization oferythrocyte quality during the refrigerated storage of whole bloodcontaining Di-(2-ethylhexyl)Phthalate.” Blood 64(6): pp. 1270-1276(1984).

We have found that most of the washing and fixation steps for alarger-scale red cell preparation can advantageously be performed in aclosed system by utilizing an appliance called the IBM 2991 Cell Washer,which was originally designed for blood banks to facilitate washing offrozen red cell units to remove cryoprotectant agents like DMSO orglycerol just prior to transfusion. The advantage to employing thisdevice for our purposes in preparing freeze-dried red blood cells isthat it provides an aseptic environment for the multiple steps ofwashing and fixation which would otherwise require handling of the redcells in an open container, and the Cell Washer induces less shearstress to resuspend the packed red cells after each step than would beexperienced with a resuspension method by hand. As an example, weintroduce into the Cell Washer processing bag a volume of 150-200 mL ofa suspension of leukodepleted red blood cells at a cell count of3-4×10⁹/mL and attach the tubing harness as described in the operatinginstructions. Then we introduce a volume of 200-250 mL phosphate washingbuffer containing 0.1% BSA sterilly through the tubing harness andperform wash cycle #1. At the end of the agitation and spinning periodprogrammed into the 2991, the supernatant washing fluid is automaticallyexpressed out to waste and fresh buffer is introduced thru the harnessfor a total of three washes. After the spinning step of the third wash,a fixation solution containing 0.05% glutaraldehyde in Hank's bufferedsalt solution [HBSS] is introduced for a timed incubation of 20 minutesat room temperature before spinning, and then three more washing stepsare performed with the phosphate buffer. At this point the fixed, washedred cell suspension is removed from the 2991 processing bag and handledin vials and bottles for the bulking and freeze-drying steps.

Combination preparations. Combination products provided herein comprisemammalian red blood cells in combination with mammalian blood platelets.The red blood cells and blood platelets may be provided together as asingle composition, or provided in separate containers in the form of akit or set, as explained further below. In either case, thecompositions, kits or sets may be used to prepare a reconstituted bloodcell preparation for use in treating subjects as described above for thesame reasons as discussed above, such as for trauma or surgery.

Thus, a further aspect of the present invention is a composition offixed-dried mammalian blood cells, the composition comprising,consisting of or consisting essentially of fixed-dried mammalian redblood cells in combination with fixed-dried mammalian blood platelets.In a preferred embodiment, the ratio by weight of red blood cells toblood platelets in the composition is between 1:0.5 or 1:1, up to aboutand 3:1 (i.e., permitting relatively more of the RBCs than platelets).Thus the present invention provides a method of administering bloodcells to a mammalian subject, comprising reconstituting such a bloodcell composition in an aqueous carrier solution (as discussed below) toproduce a reconstituted blood cell preparation, and then administeringthe reconstituted blood cell preparation to the subject Preferably, thereconstituted blood cell preparation containing from 1 or 2 up to 6, 8or 10×10⁹ red blood cells per milliliter, and from 1 or 2 up to 6, 8 or10×10⁹ blood platelets per milliliter.

It can be disadvantagous to reconstitute the red blood cells and theblood platelets together due to the heterotypic nature of the cells andcell membranes. A solution to this problem is to reconstitute thedifferent cells separately and then combine the two separatepreparations into a single preparation for administration. Hence, afurther aspect of the present invention is a kit or set comprising afirst container having a composition comprising, consisting of orconsisting essentially of fixed-dried mammalian blood cells therein anda second container having a composition comprising, consisting of orconsisting essentially of fixed-dried mammalian blood platelets therein.In one embodiment, the ratio by weight of red blood cells to bloodplatelets in the kit is between 1:0.5 or 1:1, up to 3:1. The componentsof the kit or set may be packaged together in a common package, and mayinclude (in or on the package) printed instructions for carrying out themethods of use of the kit as described below. Note that the red bloodcells and blood platelets may be used together as described below, orseparately, depending upon the needs of the particular subject. The kitor set may further contain or include a third container having anaqueous carrier/buffer solution for reconstituting both the red bloodcells and the blood platelets (it being preferred but not essential thatthe same carrier solution be used for reconstituting both the plateletsand the RBCs). Such a solution is one which is physiologicallyacceptable and in general will be sterile, preferably pyrogen-free, andwill preferably have a pH of from about 6.5 to 7.5 or 7.8. A method ofadministering blood cells to a mammalian subject with such a kit or setis generally carried out by reconstituting red blood cells as above inan aqueous carrier solution to form a reconstituted red blood cellpreparation; separately reconstituting blood platelets as describedherein in an aqueous carrier solution to form an reconstituted plateletpreparation; combining the reconstituted red blood cell preparation withthe reconstituted platelet preparation to produce a reconstituted bloodcell preparation; and then administering the reconstituted blood cellpreparation to the subject. In general, the reconstituted blood cellpreparation containing from 1 or 2 up to 6, 8 or 10×10⁹ red blood cellsper milliliter and from 1 or 2 up to 6, 8 or 10×10⁹ blood platelets permilliliter.

In the combination methods, products, kits and sets described herein,the red blood cells and platelets may be from the same or differentspecies, but are preferably from the same species. When from the samespecies, the red blood cells and the platelets may be of the same ordifferent blood type, or may be from the same or different donor. Thered blood cells and the platelets may be fixed-dried together, or may befixed-dried separately and then combined. The platelets may befixed-dried according to the procedures set forth in U.S. Pat. No.5,993,804 to Read et al., U.S. Pat. No. 5,891,393 to Read et al., orU.S. Pat. No. 5,651,966 to Read et al. (the disclosures of all patentreferences cited herein are specifically intended to be incorporated byreference herein in their entirety). In a preferred embodiment, theplatelets are characterized in that, upon reconstitution, they (a)adhere to thrombogenic surfaces; (b) do not adhere to non-thrombogenicsurfaces; (c) undergo shape change upon adhering to a thrombogenicsurface; (d) adhere to one another to form a hemostatic plug uponadhering to a thrombogenic surface; and (e) release their granularcontents.

The examples, which follow, are set forth to illustrate the presentinvention, and are not to be construed as limiting thereof. In thefollowing examples, atm means atmosphere, mm means millimeter, μL meansmicroliter, msec means millisecond, mL means milliliter, mM meansmillimolar, M means Molar, kDa means kilodalton, and temperatures aredefined in degrees Celsius.

EXAMPLE 1 Preparation of Human Lyophilized RBCs with 0.05%Glutaraldehyde (Protocol 1)

4.5 ml of human blood is drawn into a syringe with 0.5 ml CDPA-1. Theblood is then gently place into 15 ml conical centrifuge tube andcentrifuge for 10 min at 1200 rpm. The upper platelet-rich plasma layeris removed and discarded. RBCs are diluted to a Crit=5% with PBS andcentrifuged as before. The supernatant is removed and the RBCs areresuspended in the original volume of PBS for Crit=5%. Thecentrifugation is repeated and the final pellet is resuspended for aCrit=5% in PBS. Dilute 50% (v/v) freshly opened glutaraldehyde 1/1000into the RBCs for a final concentration of cross-linker=0.05% (v/v) andincubate for 20 min at 37° C. on rocker. The RBCs are centrifuged asbefore and the pellet is re suspended for a Crit=5%. The centrifugationis repeated. The final pellet is Resuspended in PBS+1% PEG 8,000 for aCrit=25%. The cross-linded RBCs are proportioned into 2 ml plasticcryovials (no more than 200 ul per vial) or 20 ml glass vials (no morethan 1 ml per vial) and frozen by placein in a −80° C. freezer. Thecells are lyophilized on a cold stage at −40° C. After lyophilization,the RBCs are stored at −20° C. for up to one year. The lyophilized RBCsare rehydrated by the original freezing volume of sterile H₂O.Examination of the cells with scanning (FIG. 2) and transmission (FIG.3) electron microscopy revealed native morphology.

The level of lysis and hemoglobin release was measured after rehydrationby centrifuging the RBCs and measuring the absorbance of hemoglobin inthe supernatant at 540 nm. Lyophilized RBCs prepared as detailed inExample 1 were compared to uncross-linked RBCs that were frozen andlyophilized and to freshly isolated (with differential centrifugation)RBCs were centrifuged. The data in Table 1 shows that lyophilized RBCsprepared as in Example 1 were essentially stable to lysis whenrehydrated. TABLE 1 EXTENT OF HEMOLYSIS OF LYOPHILIZED RBCS IN EXAMPLE 1RBC Preparation Percent Hemolysis 0.05% glutaraldehyde fixed (Example 1)0.5% 0.00% glutaraldehyde fixed  100%  Fresh cells 0.3%

EXAMPLE 2 Preparation of Human Lyophilized RBCs with1,6-diphosphofructose to Normalize Hemoglobin Oxygen Affinity (Protocol2)

The procedure in example 1 was altered by incubating the centrificallywashed RBCs with increasing concentrations of 1,6-diphosphofructose forone hour at room temperature on a rocker before adding the cross-linker,and then for an additional 20 minutes during the cross-linking step.After lyophilization and rehydration, oxygen association-disassociationcurves were measured (see FIG. 4). 10 mM 1,6-diphophofructose is thepreferred concentration to restore native oxygen ligation kinetics.

EXAMPLE 3 Occlusion of Surface Membrane by Covalent PEG 5,000 Attachment(Protocol 3)

PEG-aldehyde was prepared by dropwise adding 5 ml of 50% (w/v) PEG-amine(MW=5,000) in PBS to 5 ml of 50% (v/v; 6.29 Molar) glutaraldehyde. Theresulting solution was dialyzed thee times over a three day period vs.sodium acetate/acetic acid at pH=5.5 with a total acetate/acetic acidconcentration of 20 mM. The resulting PEG-aldehyde (5 mM PEG-aldehyde)was stored at 4° C. until use (within four weeks). Immediately beforeuse, the 5 mM PEG-aldehyde stock was diluted 1/1 with 2×PBS.

Human blood was obtained and then RBCs were isolated and freed fromplasma proteins with two centrifugational wash steps as detailed inExample 1. The RBCs were were suspended in PEG-aldehyde (2.5 mM asprepared above) for a Crit=5% after the last wash and reacted for onehour on a rocker at room temperature. Glutaraldehyde was added to themixture and allowed to react as described in Example 1. The PEGylatedRBCs were freed of reaction byproducts, lyophilized and rehydrated foranalysis as outlined in Example 1.

The thrombogenicity of RL RBC preparations was analyzed by incubatingthe lyophilized cells with human platelets, and then measuring theresulting degree of platelet activation by quantifying p-selectinpresentation of the platelet surface membrane with flow cytometry.PEG-modified RL RBCs, unmodified RL RBCs and native RBCs was compared bymixed with human platelet (11 ul) were added to fresh humanplatelet-rich plasma (1 ul) and incubated 15 minutes at roomtemperature. The platelets were then labeled by adding 20 ul ofanti-CD-61-Per CP conjugate (non-activation dependend) to identifyplatelets plus 20 ul anti-p-selectin-PE conjugate (to identify activatedplatelets). Samples were quenched and flow cytometry was performed asdetailed by Ault et al (1989) Correlated measurement of platelet releaseand aggregation in whole blood. Cytometry 10, 448-455. A comparison ofpanels A and B of FIG. 5 shows that unmodified RL RBCs partiallyactivated platelets; p-selectin was exposed to an extent approachingthat measured with ADP activated platelets. In contrast, pegylated RLRBCs (panel C, FIG. 5) did not expose P-selectin beyond the extent ofresting platelets (panel D, in FIG. 5).

In addition to the oblation of the surface thrombogenicity of RL RBCs,the covalent attachment of PEG to the lyophilized cells occludes bloodgroup antigen A. PEG-modified RL RBCs were prepared from blood group ARBCs as outlined above in this sample. The occlusion of the blood groupantigen was then followed by measuring the reactivity of the RBCs withanti-blood group A monoclonal antibody with flow cytometry. 20 ul oftype A PEG-modified RL RBCs, fresh type A RBCs and fresh type O RBCswere reacted with 20 ul of anti-blood group A-FITC conjugated monoclonalantibody (Immunocor) for 20 min at room temp. Samples were quenched andsubjected to flow cytometric analysis as detailed by Ault et al (1989)Correlated measurement of platelet release and aggregation in wholeblood. Cytometry 10, 448-455. A comparison of the middle and left panelof FIG. 6 demonstrates that covalent attachment of PEG to the surface ofRL RBCs effectively occludes the type A antigen.

EXAMPLE 4 Preparation of Lyophilized Human RBCs with DualParaformaldehyde and Glutaraldehyde Cross-Linkers for IncreasedDeformability (Protocol 4)

Rehydrated, lyophilized RBCs with enhanced deformabilities were preparedby cross-linking the cells with a dual system of paraformaldehyde andglutaraldehyde. Human RBCs were isolated and prepared for cross-linkingas described in Example 1. Instead of a 20 minute reaction with 0.05%glutaraldehyde, the RBCs were reacted first for 30 minutes withparaformaldehyde at a concentration of 0.05% (w/v). At this point,glutaraldehyde was added to the mixture for a final concentration of0.05% (v/v). After an additional 20 minute incubation with bothaldehydes, the RBCs were freed of byproducts, lyophilized and rehydratedas detailed in Example 1. When prepared in this manner, 75% of the cellswere capable of transiting a 3 micron pore size filter. TABLE 2FILTERABLITY OF LYOPHILIZED RBCs IN EXAMPLE 4¹ RBC preparation %recovery in filtrate 0.01% para, 0.01% glut. RL RBCs 75% Fresh RBCs 98%¹Fresh and RL RBCs were prepared for a Crit = 1% in PBS, then 1.0 ml wasfiltered through a 3.0 micron Millopore Isopore ™ filter with a surfacearea of 1.33 cm².

EXAMPLE 5 Preparation of Lyophilized Canine and Porcine RBCs with 0.05%Glutaraldehyde (Protocol 5)

Porcine and canine blood was isolated via venipuncture and then RBCswere isolated from other blood cells and plasma proteins as detailed forhuman RBCs in Example 1. Cross-linking, lyophilizing and rehydrationsteps were also carried out as described in Example 1. These proceduresresulted in lyophilized canine and porcine RBCs that minimally hemolysedupon rehydration. TABLE 3 EXTENT OF HEMOLYSIS OF LYOPHILIZED RBCS INEXAMPLE 5 RBC Preparation Percent Hemolysis Porcine RL RBCs (Example 5)3.7% Canine RL RBCs (Example 5) 1.2% Fresh porcine RBCs  100%  Freshcanine RBCs  100% 

The foregoing examples are illustrative of the present invention, andare not to be construed as limiting thereof. The invention is describedby the following claims, with equivalents of the claims to be includedtherein.

1. Fixed-dried mammalian red blood cells having a cell membrane, saidcell membrane including a plasticizer in an amount sufficient to enhanceor retain cell deformability at the time of subsequent reconstitution.2. The fixed-dried mammalian red blood cells according to claim 1,wherein said blood cells are human red blood cells.
 3. The fixed-driedmammalian red blood cells according to claim 1, wherein said blood cellsare selected from the group consisting of dog, cat, horse, rabbit andgoat red blood cells.
 4. The fixed-dried mammalian blood cells accordingto claim 1, produced by a process comprising: providing fixed mammalianred blood cells, then incubating said fixed mammalian red blood cellswith a plasticizer; freezing said red blood cells; and then drying saidfrozen cells to produce said fixed dried mammalian red blood cells;. 5.The fixed-dried mammalian red blood cells according to claim 4, having awater soluble polymer covalently coupled to the cell membrane thereof.6. The fixed-dried mammalian red blood cells according to claim 1, saidblood cells further having a water soluble polymer covalently coupled tosaid cell membrane thereof.
 7. A formulation comprising red blood cellsaccording to claim 1 reconstituted in an aqueous carrier solution.
 8. Amethod of administering red blood cells to a mammalian subject,comprising reconstituting red blood cells according to claim 1 in anaqueous carrier solution, and then administering said reconstituted redblood cells to said subject. 9-38. (canceled)
 39. The fixed-driedmammalian blood cells of claim 1 containing exogeneous fructose1,6-diphosphate in an amount effective to enhance the oxygen carryingcapacity thereof.
 40. The fixed-dried mammalian blood cells of claim 1,wherein said cells are dog cells.
 41. The fixed-dried mammalian bloodcells of claim 1, wherein said plasticizer is diethylhexylphthalate.